The Right Stuff
A joystick is not standard equipment for a Gulfstream GII. Neither are display screens on a console. Nor a head-up display. Sun visors to cover windows in flight would normally constitute a safety hazard. The strangest thing is the unusual accouterments present on only one-half of the cockpit. The other side is a standard GII flight deck.
This GII, N946NA, went to a special customer for an even more special purpose. The United States National Aeronautics and Space Administration—NASA—bought this and an identical GII in 1973 to serve as approach and landing trainers for space shuttle astronauts. Those two aircraft, along with two more purchased later, served NASA for 35 years, from the shuttle development stage until the program’s retirement in 2011.
Today, Shuttle Training Aircraft N946NA is the centerpiece of the Texas Air and Space Museum in Amarillo, Texas. The aircraft is the only one of the four currently on display, and space enthusiasts the world over visit this West Texas town, birthplace of shuttle astronaut Rick Husband, to tour an aircraft as unique as the shuttles themselves.
NASA engineers met a lofty challenge in creating the space shuttle. They designed a reusable space vehicle that launched like a rocket, orbited like a spacecraft and landed like a fixed-wing aircraft. Yet the shuttle flew unlike any aircraft ever built. Many refer to it as a “flying brick.” Charles Justiz proposed a more apt description: “A safe with the door open,” says Justiz, a retired NASA shuttle pilot trainer who now operates a business aircraft management service. “A brick is more aerodynamic than the shuttle.”
Training astronauts to land the shuttle required designing another engineering marvel. The Shuttle Training Aircraft, also known as an STA, needed to be reliable, durable and easy and inexpensive to maintain. And, in the spirit of the shuttle design, the trainer needed to be able to take off and cruise like an aircraft and land like the space shuttle.
“They made the STA tougher to land than the shuttle,” Justiz says. “If you could fly the STA, you could fly the orbiter.”
Plane Meets Shuttle
The pilot’s seat seemed familiar enough to Blaine Hammond as he adjusted the shoulder harness to fit his frame.
The astronaut turned Gulfstream test pilot had logged thousands of hours in the left-hand seat of a Gulfstream GII, training to land the space shuttle. But he wasn’t at the stick of the Shuttle Training Aircraft this day. He was to pilot an unmodified GII instead.
“I had all this GII time with the STA,” Hammond says, “but I realized as I sat down I’d never really flown the aircraft.”
Transforming a Gulfstream GII into an unwieldy glider required stripping away all the aircraft’s renowned grace. A comfortable cockpit was made claustrophobic. Contoured wings were marred by drag-inducing appendages. The jet engines were bridled and reined by mutated thrust reversers. The main landing gear were reinforced.
The modifications turned the smooth-flying, 60,000-pound business jet into a “semi-aerodynamic, 250,000-pound brick,” according to Hammond.
The altered wing flaps impacted lift and roll and subjected the pilot to the same gravitational forces as those experienced on the shuttle. Two side force generators mounted on the underside of the wings produced sideward movement. The thrust reversers created drag and pitch movements. The reinforced gear acted as a speed brake and induced additional drag and sideward movement.
“The shuttle had, shall we say, unique flying characteristics that weren’t easy to replicate,” Hammond says. “To take an airplane and make it fly like that unusual beast took real ingenuity.”
Grumman, Gulfstream’s parent company at the time, won the Shuttle Training Aircraft contract in 1973. NASA had a need for speed in its trainer, as the shuttle glided at more than 300 knots up until seconds before touchdown. The Gulfstream GII’s maximum operating speed of 340 knots trumped that of other business jets of the time and put it on par with larger—and more difficult to maintain—airliners and warplanes. The first two STAs were built to normal Gulfstream GII specifications in Savannah, Georgia, and flown to Grumman’s Bethpage, Long Island, facility for the retrofit. Grumman delivered the modified aircraft as STAs in 1975, six years prior to the Space Shuttle Columbia’s maiden space voyage. NASA later added two more modified GIIs as Shuttle Training Aircraft.
The STAs “performed brilliantly,” says NASA’s Justiz, even as the space agency “took the trainers to every single corner of the envelope.” That all four STAs remained operational up until the shuttle program’s discontinuation in 2011 speaks to NASA’s wisdom in choosing the GII, Justiz states.
“They had to choose a Gulfstream because the aircraft were built like a brick house and had the strength and potential growth not only in structures but in performance,” says Charles Coppi, who helped develop the Gulfstream GII as well as the Gulfstream GIII, Gulfstream GIV and Gulfstream GV. “That was exactly what NASA needed.”
"Transforming a Gulfstream GII into an unwieldy glider required stripping away all the aircraft's renowned grace."
Mastering a Difficult Approach
To appreciate the challenge astronaut pilots faced on approach and landing, stand beside a shuttle the STA was meant to mimic.
The Space Shuttle Atlantis, on permanent display at the Kennedy Space Center on the Florida coast, dwarfs all but the largest airliners. Posed at an angle, with cargo bay doors open and a mechanical arm extended, Atlantis looks like a vehicle built to orbit, never to land.
Yet Atlantis visited space and returned to earth 33 times. Each touchdown was the climax of a “short but wild ride” the STA simulated perfectly.
The shuttle returned home as a glider, decelerating below Mach 1—the speed of sound—about the same time the landing strip came within sight. Back-to-back sonic booms marked the shuttle’s subsonic arrival, and the mission commander responded by steering a sweeping, 300-degree turn, known as a Heading Alignment Cone, to line up with the runway.
Once the shuttle was aligned, the commander put the shuttle into a descent seven times steeper and 20 times faster than that of the average commercial airliner. His approach target was a point 7,500 feet/2,286 meters short of the runway. The shuttle dropped 28,000 feet/8,534 meters in a little more than a minute.
The commander pulled out of the dive and raised the shuttle’s nose as it passed below an altitude of 1,750 feet/533 meters. Fifteen seconds and 1,100 feet/335 meters from the runway, the shuttle was still going 100 knots faster than it would be at touchdown.
“If you jumped out of the shuttle when it went subsonic, it would beat you to the ground—that’s how fast it was going,” Justiz says.
Piloting an aircraft under those circumstances is “not intuitive,” shuttle astronaut Jon McBride says, nor can the experience accurately be replicated in a simulator. Hence all those hours spent in the Shuttle Training Aircraft.
Each shuttle crew included two astronauts designated to fly the orbiter: a commander and a pilot. The commander maneuvered the shuttle and handled the approach and landing. The pilot assisted the commander and led satellite release and recovery jobs in space. Commanders typically performed 1,200 simulated landings in the Shuttle Training Aircraft in advance of their first mission while pilots executed at least 750 mock touchdowns.
The astronauts did 10 approaches per training session. The runs were conducted monthly, with the frequency increasing as the launch date approached—twice a month within six months of liftoff; once a week in the month leading up to the mission.
Each simulated approach, or profile, started at 35,000 feet/10,668 meters. The instructor, seated in the co-pilot’s seat of the STA, and the flight engineer, seated between and behind the astronaut and the instructor, engaged the computer program that instantly turned jet to cracked-open safe. The STA was now the shuttle, at least in the way it reacted to the controls.
All shuttle flyers were once “fighter jocks”—military aircraft pilots—and adjusted intuitively to the shuttle’s unique handling characteristics. Those conditions can be replicated in flight simulators. The challenge, and the reason for the intense approach-and-landing training in the STA, was dealing with what NASA instructor Kenneth Bakers calls “different energy situations.”
The shuttle engines were not used on approach and landing. The shuttle was truly a glider. Bleed off too much energy on approach, and the shuttle may not make the landing strip. Fail to scrub enough speed and the shuttle may overshoot the runway, because the glider lacked the ability to circle and make another approach. Complicating the task, the optimal touchdown speed tested the limits of the tires. The commander couldn’t “land hot and count on a long rollout,” Justiz says. “The parameters, the margin for error, were very tight.”
The simulated landings in the STA came with a surreal element. The trainer is much smaller than the shuttle, and the trainer’s cockpit is approximately 25 feet/7.62 meters closer to the ground on landing than the shuttle’s. The simulation ends with the STA still well off the ground as a result. The instructor takes control of the aircraft at that point, climbs and prepares for another simulated approach.
“An STA landing is the smoothest landing you’ll ever make,” Hammond jokes.
"If you jumped out of the shuttle when it went subsonic, it would beat you to the ground—that's how fast it was going."
Tough and Ready
As museum relics go, the STA on display in Amarillo is in pristine condition.
The cabin carpet is a little threadbare and the coffee maker in the galley won’t ever brew another cup, but for an aircraft that flew tens of thousands of airframe-stressing hours over a 35-year period, it looks ready for its next astronaut trainee.
“It was a real workhorse,” says Ron Fernuik, director of the Texas Air and Space Museum.
The STAs endured more wear and tear than a pair of favorite sneakers. The shuttle program was still young when the original two trainers reached the end of the service lives recommended by Grumman. Extensive fatigue and structural tests confirmed Coppi’s “built like a brick house” assessment, and NASA continued to operate the original STAs while adding two more in the 1980s. The GIIs were so rugged the newest aircraft in the STA fleet started out as a test platform for another NASA project involving propfan technology.
The STAs’ durability speaks to the “Iron Works” nickname bestowed on Grumman and Gulfstream at the time of the Gulfstream GII’s development.
“We beat on those aircraft; the GII was an incredible choice,” Justiz says. “Those were invaluable aircraft.”
The STAs performed even on supposed days off—shuttle launch and landing dates. NASA personnel would “shoot approaches” aboard an STA to assess wind, weather and visibility conditions in advance of takeoffs and landings. The tests were particularly important at launches, since the “shuttle stack”—as the two rocket boosters, fuel tank and shuttle together were known—was susceptible to wind shear. The boosters were also fragile. Mission-scrubbing malfunctions that could force the shuttle to return to the ground prior to reaching orbit were a constant concern.
“The fact that a space shuttle never lifted off the pad or landed without a Gulfstream in the air says something,” says Fred Karst, director, Service Engineering, Gulfstream, and the company’s resident NASA aficionado. “NASA uses other airplanes, but when it’s high-profile, it has to be a Gulfstream.”
Gulfstream and NASA: Innovation
Gulfstream Aerospace and America’s space agency have a long history of collaboration. Gulfstream’s original parent company, Grumman, built the Apollo Lunar Module that brought man to the moon, and NASA has utilized Gulfstream aircraft as trainers, transports, and research and testing platforms for close to 50 years.
“NASA ‘married up’ to Gulfstream,” says Blaine Hammond, a former NASA astronaut who now works as a Gulfstream test pilot. “When you find a well-organized company that is safe and has good performance margins, you stay with them.”
Among the many projects Gulfstream and NASA have partnered on are:
SYNTHETIC VISION: NASA engineers pioneered Synthetic Vision research starting in the 1980s. Synthetic Vision Systems are designed to significantly improve pilot situational awareness. NASA tested its system in 2004 using a Gulfstream GV. Gulfstream announced plans for a Synthetic Vision-Primary Flight Display system in 2006 and introduced it two years later.
PROPFAN: NASA purchased a Gulfstream GII in the 1980s and modified it to be used as a test platform for propfan engine technology. A propfan blends jet engine concepts with a propeller mounted on the front of an engine unit. The design goal is to generate the speed and performance of a turbofan jet engine with the fuel economy of a turboprop. NASA mounted a propfan engine on the left wing of the GII and reinforced the fuselage with a steel sleeve to protect the test engineers inside. The GII propfan aircraft was later converted to a Shuttle Training Aircraft.
UAVSAR: NASA mounted an Unmanned Air Vehicle Synthetic Aperture Radar to the underside of its Gulfstream GIII atmospheric research test platform. The UAVSAR can measure ground deformations to within inches, useful in mapping earthquake fault lines and collecting other geological data.
ACTIVE COMPLIANT TRAILING EDGE: NASA replaced the conventional aluminum wing flaps of its Gulfstream GIII aerodynamics research test platform with composite flaps designed to continuously bend in the airstream. The aim of the research, which is ongoing, is to develop flaps that will be significantly quieter during takeoff, approach and landing.
LIDAR MAPPING: NASA’s partners, the National Science Foundation and the National Center for Atmospheric Research, operate a Gulfstream GV for environmental research. The aircraft has conducted LIDAR surveys of Antarctica and the Arctic. LIDAR technology measures distances using a laser and analyzing the reflected light. The GV’s high-altitude capabilities also allow researchers to collect data on storms and the lower edge of the stratosphere.
CORROSION RESEARCH: Gulfstream utilized NASA’s Atmosphere Exposure Test Facility, located on the beach along the Kennedy Space Center property in Cape Canaveral, Florida, to assess the adverse effects of corrosion on aluminum airframes.
SUPERSONICS: Gulfstream partnered with NASA in testing its “Quiet Spike” sonic boom mitigator. The Quiet Spike, a telescoping pole that mounts on an aircraft’s nose, softens the shock waves produced by breaking the sound barrier by spreading the waves over the length of the aircraft. The result is three small shock waves that travel parallel all the way to the ground and transform a sharp crack into a quiet whisper. The research, conducted using a NASA F-15 fighter research aircraft at NASA’s Dryden Flight Research Center in California, is vital to the development of a supersonic business jet.
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